This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We propose a research program at SSRL on water across the phase diagram and in different chemical surroundings using X-ray Raman Spectroscopy (XRS) in combination with theoretical simulations to gain new unique information on the local structure of water. We plan to measure XRS spectra at a number of different temperatures from the supercooled region (-20[unreadable]C) to well above the boiling point (200[unreadable]C) and pressures up to 400 MPa. Furthermore, we will investigate a number of aqueous solutions at various concentrations with different mono-, di- and trivalent cations and different monovalent anions. The structure of water in biological systems will also be addressed in, e.g., reverse micelles. This extensive dataset of local water structure is needed for a firm theoretical analysis and for comparing the results with the existing data using other techniques, in order to get an improved and detailed understanding of the local structure of water and how it varies with thermodynamic and chemical conditions.